The present invention relates generally to coated substrates and methods of coating the same. In preferred embodiments, the present invention relates to transparent substrates having an anti-reflective hydrophobic (water repellant) coating thereon.
Glass is typically made of silicates that are melted to form a clear, transparent, solid material. The fundamental molecular structural unit of conventional glass is a SiO4 tetrahedron. Ordinary float glass (named for its production process whereby a molten ribbon of glass is floated on molten metal to provide a smooth surface) includes additional amounts of soda (Na2O), usually in the form of sodium carbonate or nitrate during the production process, lime (CaO) and other oxides (usually aluminum and magnesium oxides) to form a soda-lime-silica structure known colloquially as soda-lime glass. Other specialized glass can be prepared by the introduction of other additives and constituents.
It is sometimes highly desirable for conventional glass to have hydrophobic (water repellant) surface properties when employed in certain end-use applications, such as for automotive window glass. Various proposals exist to impart hydrophobic (water-repellant) properties to glass substrates. For example, U.S. Pat. Nos. 4,263,350, 4,274,856, 5,665,424 and 5,723,172 (the entire content of each being incorporated expressly hereinto by reference) disclose generally that glass surfaces can be coated with a vapor deposited layer of an chloroalkylsilane, such as dimethyldichlorosilane (DMDCS) so as to improve their hydrophobicity and/or release properties. Other proposals exist whereby a fluoroalkylsilane (FAS) coating may be employed to xe2x80x9ccapxe2x80x9d an underlayer on a glass substrate so as to improve coating durability. Please see in this regard, U.S. Pat. Nos. 5,328,768, 5,372,851, 5,380,585 and 5,580,605 (the entire content of each being incorporated expressly hereinto by reference). In addition, International Application WO 00/25938 (the entire content of which is expressly incorporated hereinto by reference) discloses that a silicon film consisting of chains of siloxane groups each terminating in an end molecule which reacts with water to form an OH group, may be capped by further reaction of that OH group with trimethylchlorosilane to form trimethylchlorosiloxane.
In commonly owned, U.S. patent application Ser. No. 09/921,303, filed on Feb. 1, 2001 (the entire content of which is expressly incorporated hereinto by reference) there are disclosed coated substrates (preferably glass) and methods which exhibit improved hydrophobicity and durability. In some of the especially preferred embodiments of the present invention, coated substrates and methods are provided which include an SiOx-containing anchor layer comprised of a controllably humidified vapor phase deposition of a chlorosilyl group containing compound (most preferably silicone tetrachloride), and a hydrophobic capping layer chemically bonded to the SiOx-containing anchor layer.
It has now been discovered that coated substrates of the type disclosed and claimed in the above-identified U.S. application Ser. No. 09/921,303 may also be rendered anti-reflective. Thus, according to one aspect of this invention, substrates may be provided with an anti-reflective hydrophobic surface coating comprised of the reaction products of a chlorosilyl group containing compound and an alkylsilane. Most preferably the substrate is glass. In one preferred form of the invention, highly durable hydrophobic coatings may be formed by forming a silicon oxide anchor layer from a humidified reaction product of silicon tetrachloride, followed by the vapor-deposition of a chloroalkylsilane, preferably dimethyldichlorosilane (DMDCS). The layer thicknesses of the anchor layer and the overlayer are such that the coating exhibits light reflectance of less than about 1.5% (more preferably less than about 1.0%) at a wavelength of about 525 nm (+/xe2x88x92 about 50 nm).
These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.